Realising that the recent spread of the dengue virus in the districts and in the city could spell disaster in the post-puja days ~ particularly if two different types of dengue viruses are circulating in the state ~ the state health department has taken an initiative to detect the virus types. The department has decided to join hands with the city-based virus unit of the Indian Council of Medical Research (ICMR) for detection of the dengue viruses circulating in Kolkata and the districts. Over the past three years, many Kolkatans have developed an antibody to fight D3 serotype dengue as that particular strain of the virus has been circulating in the city since 2005. But a number of people from the districts visited the city during the pujas, increasing the likelihood of a new type of dengue virus having been introduced here. If that has indeed happened, the city could be in for serious trouble. The situation is being considered critical because the type of virus circulating in the districts is yet to be identified. Recently, The Statesman had published a report pointing out that ICMR scientists foresaw a disaster in the post-puja days if the dengue viruses in the state were found to be of multiple types. They said if a new type of dengue virus infects an individual who had suffered from dengue before, the existing antibody fights the new virus, causing haemorrhage. The dual infection is fatal, for dengue kills when haemorrhage begins. A senior health department official told The Statesman that the effort to identify the types of dengue viruses has been initiated after it was found that dengue has spread rapidly in the adjoining districts of Kolkata. He also made it clear that the initiative has been taken to find out whether two different types of viruses are circulating in the districts as well as Kolkata. There are four dengue serotypes ~ D1, D2, D3 and D4 ~ each with a different genetic arrangement. Over the past three years, D3 virus has been in circulation in the city.